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DAN Y-40 Test on Deep Stops. Lower bubble count?

Discussion in 'Technical Diving Specialties' started by Macan, Oct 21, 2020.

  1. Macan

    Macan Tech Instructor

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    See starting 34:07 of this video from DAN. Their Y-40 study shows that the deep stop divers have a significantly lower bubble count than shallow stop divers? I expected the opposite. What GF were the Deep and Shallow stop divers using? Sorry if this was already discussed in another thread.


     
  2. jlcnuke

    jlcnuke Solo Diver

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    According to the comment from Dr. Simon Mitchell, it appears that the "deep" profile was a GF low of 50 with a GF high of 100 and the shallow profile was a GF low of 100 and a GF high of 100.
     
    Macan likes this.
  3. jvogt

    jvogt ScubaBoard Sponsor ScubaBoard Sponsor

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    Although the ascent times match these GFs fairly close, these where not Buehlman profiles. Most notably the 6 meter stop was quite a bit longer than the 3 meter stop. This is going to make a big difference when using 50% for deco.
     
    Macan likes this.
  4. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

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    GF low of 50 is not "deep"
    GF high of 100 is nuts
     
  5. jlcnuke

    jlcnuke Solo Diver

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    I agree. I really liked the comment from Dr. Simon Mitchell on the video:

    I think there's still some good science left to be done on determining an optimal GF low for "average" tech divers yet. Not sure when we'll get more information on that at this point though.
     
    DivingColeridge and Macan like this.
  6. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

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    Its going to be expensive and potentially not generalized across different ages, genders, or even depth or dives.

    GFs are linear and DCS risk almost for sure isn't. At least right now you still have some luddites using VPM+1 (or various old forms of ratio deco) and then it runs the gament up to GFs of 80/90 or thereabouts. Personally I'm happy with 50/75 unless I'm feeling really far from help in which case I drop to 50/70
     
  7. jlcnuke

    jlcnuke Solo Diver

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    Yeah, hence why I don't see a lot of new info coming out soon. I'm running 30/70 for now, as that's what we used for AN/DP, but plan on moving the GF low up to 50 progressively based on the studying I've been doing.
     
  8. NothingClever

    NothingClever ScubaBoard Sponsor ScubaBoard Sponsor

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    I just watched this video a few nights ago. Dr. Marroni is clearly a smart man and he presented some compelling data but I have to say the contrary trajectory puzzled me and made me wonder how much DAN stipulated a peer review before publishing (broadcasting).
     
  9. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

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    30 low is on the deeper side but unless you are doing 60+mins moving up to 50 low is all within the margin of error anyway.

    3 or 5 more mins at intermediate stops is inconsequential in the grand scheme of things. 3 hrs of deco total with 25mins shifted "deeper" is categorically a different kind of dive than 25mins total of AN/DP level deco. For many tech1 or AN/DP level dives (150ft for 25mins) the first stop isnt even at the 70ft EAN50 switch yet no matter what GF low you choose.
     
    ls23, Macan and ChuckP like this.
  10. NothingClever

    NothingClever ScubaBoard Sponsor ScubaBoard Sponsor

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    @jlcnuke - Could you please point out where did Dr. Mitchell wrote that? I’m interested to locate it so I can absorb the context and circulate it (full attribution to Dr. Mitchell) amongst folks here in Saudi Arabia who just posted the Dr Marroni video.
     

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